IEEE 802.11 is a set of media access control (MAC) and physical layer (PHY) specification for implementing wireless local area network (WLAN) communication in the Wi-Fi (2.4, 3.6, 5, and 60 GHz) frequency bands. The 802.11 family consists of a series of half-duplex over-the-air modulation techniques that use the same basic protocol. The standards and amendments provide the basis for wireless network products using the Wi-Fi frequency bands. For example, IEEE 802.11n is an amendment that improves upon the previous IEEE 802.11 standards by adding multiple-input multiple-output antennas (MIMO). IEEE 802.11ac is an amendment to IEEE 802.11 that builds on 802.11n. Changes compared to 802.11n include wider channels (80 or 160 MHz versus 40 MHz) in the 5 GHz band, more spatial streams (up to eight versus four), higher-order modulation (up to 256-QAM vs. 64-QAM), and the addition of Multi-user MIMO (MU-MIMO). IEEE 802.11ad is an amendment that defines a new physical layer for 802.11 networks to operate in the 60 GHz millimeter wave spectrum. This frequency band has significantly different propagation characteristics than the 2.4 GHz and 5 GHz bands where Wi-Fi networks operate. IEEE 802.11ah defines a WLAN system operating at sub 1 GHz license-exempt bands. 802.11ah can provide improved transmission range compared with the conventional 802.11 WLANs operating in the 2.4 GHz and 5 GHz bands. 802.11ah can be used for various purposes including large-scale sensor networks, extended range hotspot, and outdoor Wi-Fi for cellular traffic offloading, whereas the available bandwidth is relatively narrow. IEEE 802.11ax is the successor to 802.11ac; it will increase the efficiency of WLAN networks. IEEE 802.11ax is currently at a very early stage of development and has the goal of providing 4× the throughput of 802.11ac.
Beacon frame is one of the management frames in IEEE 802.11-based WLANs. Beacon frame contains all the necessary information about the network. Beacon frames are transmitted periodically to announce the presence of a wireless LAN. Beacon frames are transmitted by an Access Point (AP) that manages an infrastructure Basic Service Set (BSS). Beacon frames consist of MAC header, Frame body and FCS. Typical fields include timestamp, beacon interval, capability information, SSID, supported rates, and other parameter sets. The AP can manage the network loading of the BSS by broadcasting the following information: channel load information, BSS load information, BSS available admission capacity, BSS average access delay, and extended BSS load element.
A wireless station (STA) uses the above information to select the best AP among all the reachable APs to join a specific WLAN or BSS. Studies show that in a dense environment, an STA joins a BSS only for a few minutes. Due to bursty user application behavior, about 10% of the STAs will leave a BSS less than two minutes after association. The departing STAs trigger Group Temporal Key (GTK) handshake. Further, less than 30% of STAs will stay in a BSS over 60 minutes. Under such dense environment with bursty user application behavior, a solution is sought for effective BSS load management.